People who have a very rare form of autism may benefit from treatment with a common nutritional supplement, a new study suggests.
The results show some people who have symptoms of both autism and epilepsy have a rare genetic mutation that causes them to have abnormally low levels of essential nutrients called branched-chain amino acids (BCAAs).
When the researchers fed a diet enriched with BCAAs to mice that were engineered to have that same genetic mutation, the diet completely reversed the symptoms, the researchers said. The mice not fed the enriched diet showed the symptoms of epilepsy and other neurological problems.
However, it's not clear whether the findings will translate to people. Because the mutation is so rare, the researchers have not yet studied the effects of adding BCAA supplements to the diet of people with this particular form of autism, and it's possible a change in diet may only be beneficial if started early in life (the patients currently known to have the mutation are no longer young children).
Still, the findings suggest there may be other forms of autism with genetic causes that can be treated, "and we need to find them," said study researcher Gaia Novarino, a staff scientist at the University of California, San Diego.
Patients could also be screened for the new genetic mutation, or related mutations, to predict whether they will develop the disease, the researchers said.
The study is published online today (Sept. 6) in the journal Science.
The researchers analyzed genetic information from individuals in three families of Turkish, Egyptian or Libyan descent, all of whom had children with autism, intellectual disability, and either seizures or abnormal brain wave activity. The families were consanguineous, meaning the parents were closely related by blood. (Children of closely related individuals are known to be at increased risk for genetic disorders.)
Six of the children had mutations in a gene called BCKDK. In contrast, none of the 200 healthy people tested for the study had the mutation.
The result of this mutation is that the body breaks down BCAAs more rapidly than normal. Indeed, the children in the study with the mutation all had below-normal BCAA levels. Their BCAA levels could be increased without ill effects by providing them with BCAA supplements bought from a health food store, the researchers said.
The researchers next need to study whether the patients' seizures and autism symptoms improve with the nutritional supplement, a process that could take some time. They will need to find more people with this mutation in order for their study to have scientifically meaningful results.
"It's really encouraging from the point of view of treatment," said Valerie Hu, a professor of biochemistry and molecular biology at George Washington University, who researches the genetics of autism and was not involved in the study. "It shows that some forms of autism ... [are] a result of some metabolic dysfunction," Hu said.
Hu said that, as a mother of a child with autism, the search for a cure often can seem hopeless. "When you think that this disorder is a result of faulty brain development, what are you going to do about that?" Hu said.
But if studies show that some types of autism are due to metabolic abnormities, it makes sense that correcting such abnormities could improve symptoms, Hu said.
The UC San Diego researchers suspect the BCKDK mutation causes both seizures and neurological problems. It's possible that because levels of BCAAs are low, a higher concentration of other amino acids find their way into the brain and cause problems, the researchers said.
Finding that a mental condition is caused by a metabolic problem is not unprecedented. The condition phenylketonuria, or PKU, occurs when the body cannot properly break down the amino acid phenylalanine. Levels of this amino acid can build up and cause brain damage — leading to symptoms such as seizures and mental retardation, according to the National Institutes of Health. The condition is treatable if children follow a strict diet with low levels of phenylalanine.
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